Such valve devices serve to provide pressure control for hydraulic actuators, for example, in control systems for automatic gearboxes, or for regulating the pressure in a control chamber of a variable oil pump of an oil circuit for lubricating units and an internal combustion engine of a motor vehicle. A ring of a discharge chamber upon which a rotor of a vane pump or a gear pump rolls off is displaced or turned via the pressure in the control chamber, thereby regulating the volume flow.
The pressure control valves used for this purpose are configured as multi-way solenoid valves by means of which the pump control chamber can either be relieved via the oil sump or loaded by means of an additional pressure from the discharge pressure of the oil pump. Pressure relief valves are also frequently installed in the control loop which delimit the maximum discharge pressure.
Such a system for controlling the pressure in two control chambers of an oil pump having a solenoid valve is described, for example, in DE 11 2008 000 978 T5. The differential pressure between the two control chambers is changed depending on the discharge pressure and the position of the regulating slide of the solenoid valve. This system also comprises a pressure relief valve via which the oil from the discharge side of the pump can be returned to the suction side if an excessive discharge pressure prevails. The use of an additional pressure relief valve is a drawback.
A solenoid valve integrating the function of the pressure relief valve for an oil pump adapted to be regulated via a control chamber is described in DE 10 2010 025 171 A1. This solenoid valve comprises an electromagnetically operable valve member connected with the armature, which valve member either blocks a passage from the inlet port to the control chamber pressure port connected with the control chamber of the oil pump, or a passage from the control chamber port to the outlet port, depending on the energization of the solenoid valve. The pressure at the control chamber pressure port and thus in the control chamber of the pump is thereby either increased or decreased depending on the required volume flow of the oil pump. The discharge pressure also acts upon the valve member so that a force is produced which moves the valve member into the position in which the connection of the control chamber pressure port to the outlet port is established when the force exceeds a maximum allowable value.
EP 2 031 475 A2 describes a pressure control valve where a regulating slide is mounted in an axially movable manner in the valve housing, the regulating slide being spring-loaded from both axial ends. The ports are defined by transverse bores in the housing, wherein the control chamber pressure port is arranged between the discharge pressure port and the outlet port which is defined at the side of the valve housing remote from the actuator unit.
These valves either have no pressure relief functions, or the pressure relief function is directly dependent on the outlet pressure of the pump. This may lead to a poor oil supply of the internal combustion engine at high flow resistances in the circuit. There is also no regulating pressure feedback via the pressure applied to the internal combustion engine.